Method or process of freezing



Rarented Mar. 27, 1934 METHOD on PROCESS or FREEZING Benjamin S. Foss, Brook line, Mass v assignor to B. F. Sturtevant Company, Hyde Park, Mass, a corporation of Massachusetts No Drawing. Application November 2, 1929 Serial No. 404,526

2 Claims. (Cl. 99-14) The present invention relates to a method or process of treating foods and other material.

In -the freezing or solidification of foods or other material by the abstraction of heat, it has been found that where such freezing or solidification takes place with comparative slowness so that it extends over a substantial period of time, objectionable changes take place in the food or material, due to thejormation of ice crystals which rupture the cells, ing down the structure and per thereby breakmitting the escape of the juices, as in the caseof foods like fish, or due to the separation of the constituents of the material, as for example, the crystallizing out of the sugar late, or the formation of ice fro fruit juices.

from molten sweetened chocom the water of If instead of freezing or solidifying food or other materials at a slow rate, this is done very quickly, these objectionable changes in the food or material may be avoided and freezing or solidification will be effected without changes or alterations in the cell structure or character or composition of sult, all of the original flavor of the material being treated. As a rethe food will be preserved and the composition and character of the food or other material retained in its original form.

To the above end the present invention con-' sists in subjecting the food or other material to the action of a gas at a sufficiently low temperature to cause freezing with such rapidity that the structure and composition of retained in its original form.

the material is A further feature of the present invention consists in the use of gas saturated with water or other liquid, thereby to prevent the drying of the material being frozen.

According to the present invention the food or other material is frozen by subjecting it, preferably while unwrapped or unpackaged, to the direct action of a blast or high velocity current of gas at low temperature, preferably minus 40 F. to minus 60 F.

ing the food or material to be Gas at this temperature strikfrozen at high velocity abstracts the heat with great rapidity,

causing the quick freezing so necessary for the retention of the original flavor, composition of the food or other Preferably the velocity of the gas structure. and material.

ill be from one thousand to three thousand feet er minute. ordinarily preferring the highest possible velocity which will not injure or displace the material to be frozen; in order to eilicient manner theturbulent fl secure in most ow necessary to mately minus 40 rect contact v. ith

cause the immediate sweeping away from the surface of the food of the film of gas in contact therewith and the presentation of fresh gas,

thereby obtaining the the food to the gas ne rapid transfer of heat from cessary for quick freezing.

Among the difficulties present when it is attemptedto freeze by means of a gas-such as air,

is the drying or desiccating effect upon the food or material being frozen. Air at F. and below has a very considerable capacity for absorption of moisture, and unless saturated, will absorb it from any exposed moist surface even at this'low temperature. Even at minus and minus F., air has a substantial capacity for moisture and will absorb the same, although to a lesser extent, whenever the opportunity offers. Since this capacity of air for moisture increases with each degree of rise in temperature, any warming of the air by the transfer of heat from the material to be frozen increases the drying tendency of the air. Even at as low temperatures as minus 10 and minus 20 F'.

a slight increasein' temperature of the air results in a very material increase in moisture absorbing ability of the air with consequent drying of the food.

I have found that at'temperatures of approxi- F. air for moisture is and lower, the capacity of practically nil so that air at such a low temperature is unable to take up moisture from an exposed moist surface. Furthermore, since air at minus 40 F. and lower contains and can contain practically no moisture,

any slight warming transfer of heat in of the air by reason of the the freezing operation has no appreciable effect to increase the moisture capacity so as Accordingly,

to produce any substantial drying. the use of a gas, such as air for example, at a temperature approximately minus 40 F. or lower not only secures quick freezing of the food with the retention of all the original flavor and structure, but also avoids the possibility of drying or desiccating of the. food or other material being frozen. Thus I am enabled to freeze fish, meats, and similar foods having exposed moisture-bea ping or vent the absorption the drying thereof. f

It will be observed low temperature of and the high velocity the gas ring surfaces without wrappackaging or in any way preparing or handling the food or employing liquids in dithe food or otherwise to preof moisture therefrom and that due to the extremely which is employed turbulent flow with the consequent rapid transfer of heat from the food to the gas, there is an almost instantaneous freezing of the exposed outer surface. Such immediate surface freezing forms a protective 'layer envelope or case hardening as it might be termed, which tends to retain within the food all the original moisture, effectively preventing its escape from thesurface. Thus, even in the event of a substantial increase in temperature of the gas, due to the transfer of heat or otherwise, with resulting increased capacity for moisture, there can be no drying of the interior of the food or material.

After the food or other material is frozen it may be wrapped or packaged if frozen unwrapped) and may be kept for long periods if maintained at proper temperature.

While I prefer to operate at temperatures so low that thegas has practically no ability or capacity to absorb moisture, there may be conditions, due to the character of the material being frozen or otherwise, where it may be necessary or desirable to use gas at a temperature at which it will have a substantial capacity for moisture. Under such circumstances the gas will be saturated with moisture previous to its application to the material to be frozen, thereby preventing any further absorption of moisture at the temperature of ap 'plication. Inasmuch as the gas is supplied in sufficient volume and velocity so that only a minimum rise in temperature of the air is permitted, the drying effect will be negligible, so far as certain classes of foods and materials are concerned.

While ordinarily atmospheric air will be used as the freezing medium, it is obvious that other gases, vapors and mixtures of the same, might be employed, for example, gases like hydrogen hav-' ing a high specific heat. Its capacity for absorbing a large amount of heat per unit of weight might, under certain circumstances, prove desirable, or a nonoxidizing gas or germicidal gas, as conditions required. Also, vapors of oils or other ingredients of the material to be frozen employed at approximately atmospheric pressure,

or slight'ry above or below such pressure, it may be desirable at times to use pressures substantially higher or lower than atmospheric pressure.

Nor is the present invention limited to air or other gas alone as the freezing medium since in its broader aspects it includes the use in connection with such air or gas of the vapors not only of water but also of other liquids 01' substances in kind and amount to suit the particular conditions of the material being frozen.

Having thus described the invention, what is claimed is:

1. The process of treating food and other material which consists in subjecting the material to the direct action of a gas at a temperature not substantiallyabove minus 40 degrees F. and at a velocity not less than approximately one thousand feet per minute.

2. The process of treating food and other material which consists in exposing the same to the action of a gas at a temperature not above approximately minus 40 degrees F. and at a velocity sufficiently high to produce the turbulent flow thereof whereby quick freezing of the material will be secured without appreciable increase in temperature of the gas with resultant desiccation.

BENJAMIN S. FOSS. 

